Means for controlling and equalizing tube temperatures



EQUALIZING umns FOR I TUBE TEMPERATURE Filed Jan. 1,- 1945 WWW;

c. c: .wA'rsoN 2,458,756 CONTROLLING AND I (karles 67 (M82 so Patented Jan. 11, 1949 MEANS FOR CONTROLLING AND EQUALIZ- ING TUBE TEMPERATURES Charles 0. Watson, Evanston, Ill., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware Application January 1,, 1945, Serial No. 570,990 2 Claims. (Cl. 257-228) This invention relates to a means of equalizing temperatures in the tubes of a tube bank within a heat exchange chamber, or more specifically a means for eliminating thetemperature differential between the outer tubes and the inner tubes of a relatively compact bank of tubes; the temperature differential resulting from the cooling effect of the exterior walls of the enclosing chamber.

Within any cell or chamber having a group or bank of tubes there is always some inequality of heat supply to or from the outside tubes of the bank as compared to the inner tubes of the bank. Even though well insulated, the exterior walls will be cooler than the heating medium circulating through the chamber, due to conduction and radiction losses. Air infiltration also will account for lower temperatures along the outside walls of some types of chambers, such as those employing low pressures and bolted panel type of construction.

The object of this invention is to substantially eliminate the cooling eifect of exterior chamber walls on a tube bank. This may be accomplished by placing a jacket or plates Just inside and spaced slightly away from the chamber wall or walls in order to allow a regulated amount of heating medium to flow into the space therebetween. The regulation or control of the flow of heating medium to this space is made by a slidable slotted strip, which when moved longitudinally will open and close a series of orifice slots provided at the upstream end of the jacketed space.

This invention is very useful, for instance in connection with the reactor cell of a butane dehydrogenation unit where the endothermic heat' for processing, required by the catalytic reactor tubes contained therein, is supplied by hot combustion or'flue gases passed through the cell, while for the reactivating process, less-hot flue gases are supplied to carry away exothermic heat from the tubes in the cell. The construction of the cell and tube bank is such that thehot gases are channeled into individual sleeves placed around each tube in the group, and do not flow through the body of the chamber itself. The tubes and sleeves adjacent the outside walls of the chamber, therefore, will contribute the greater part of the heat loss to the walls, and thus be cooler than the interior tubes. This inequality of heating in the reactor tubes is very undesirable resulting in a, non-uniform product obtained invention may be used to substantially eliminate unequal tube temperatures, is rectangular in shape and has the reactor tubes vertically positioned. The walls are of a hard-surfaced insulating block with a sheet metal casing on the outside. For this type of cell, vertical jacket plates may be suspended from an upper horizontal partition plate along each of the exterior walls of the cell, and will be spaced slightly away from the inside surface of the insulatin block, say approximately one inch. Narrow slots may then be placed in the horizontal partition plate just'above this space provided between the jacket and outer wall in order to admit the hot gases to this space, A movable bar with correspondingly spaced slots may be provided to slide on the partition plate above the fixed slots, such that adjustability can be given to the amount of heating medium flowing to the jacketed space. It is further contemplated that a rod, or some type of extension attached to the slide bar, will pass through the cell wall and provide means for opening and closing the gas inlet slots from the outside of the reactor chamber.

While the above discussion points out the particular adaptability of the invention to the butane dehydrogenation reactor chamber, it is not intended to limit the invention to this type of unit only, since other tubular-containing cells and chambers may well make use of the improvement to equalize tube temperatures.

Briefly the invention comprises placing inner plates or a jacket inside and spaced away from the exterior walls of a chamber containing a bank of tubular members therein, and providing means for admitting and regulating flow of a heating and/or coolin medium to the space provided, in order to maintain the temperature of all exterior tubes substantially equal to that of all the interior tubes of the bank.

The features and operation of the improvement comprising this invention will be more apparent with reference to the accompanying drawing.

Figure 1 shows in cross-sectional elevation a chamber containing a bank of tubes, and the added features for temperature equalizing comprising this invention.

Flgure -2 shows a partial-sectional plan of the chamber and tubes as indicated by the line 2-2 of Figure 1.

Figure 3 shows an enlarged detail of a portion of the chamber indicated by line 3-3 in Figure 2.

Figure 4 is an enlarged perspective view of a portion of the slide bar member I5 of Figure 3.

Referring now to Figure 1, the numeral l is given to each of the tubular elements of a tube bank passing through a cellor chamber 2. Around each tubular element I is placed a sleeve 8, such that an annular space is provided for hot combustion gases to enter, as indicated by the arrows. The heating gases enter the top of the cell through an inlet duct 1. For the cell shown the walls are constructed of a thick block-type of insulation 5 and sheet metal casing plates 6. An upper tube sheet I and a. lower tube sheet 8 may be castings and serve to support the tubes I. A horizontal baflle sheet 9 is continuous through the entire cell 2 and serves to block the flow of hot gases through the cell and around the outside of the sleeves 8. The angle-shaped members I and I 0' are continuous around the periphery of the cell 2 and serve to hold sand II or some similar packing material to provide a seal against gas flow at these points. A Jacket sheet I2 which comprises one of the features of this invention is suspended from the sand-holding member I0 and should be continuous around the inside of all exterior walls. This Jacket I2 is spaced somewhat away from the inner surface of the insulating wall providing thereby a space It for flow of the heating gas. It should be noted that the jacket sheet I2 stops short of the bottom of the cell 2 in order to provide space and means for discharging the heating medium. The hot gases are removed fromthe cell 2 by means of outlet duct t. Another feature of this invention is the continuous series of slots H placed in the seal member Ill just above the space ill, in order to admit hot gases to this space It. Above the slots It in the seal plate or plates It are it follows that all of the sleeves 3 and all the placed slidable strips I5, one for each exterior wall. The strips it are perforated with slots It to match the slots I4 in the plates Ill, such that these strips I5 may act as valves to regulate heat flow to the space it. Rods it are attached to the slide strips I5 and should extend through the exterior walls to provide a means exterior from the chamber for pushing or pulling the valve strip I5. A retainer or separating strip I! to hold the sand II is provided at the walls having the Jacket I2 and the' hot gas inlet in order to have space for the inlet slots and the control valve strip I5.

Referring now to Figure 2, a partial plan vie of the cell and tubes is shown at the plane cut by the line 2-2. Slide rods it which are attached to the slide strips it are shown on the side and end walls of the cell 2. Handles I8 may be placed on the ends of the rods I8 which project through the chamber walls 5, for convenience in grasping, for adjustment of hot gas flow to the space I3. It is, of course, possible to provide mechanical means, gearing and the like, if it is so desired, for controlling the movement of the rod I6 and strip I5. A sleeve or a packing gland I8 should be provided through the walls 5 for each of the rods I6.

Figure 3 shows an enlarged view of a portion of the cell in cross-section at the slide bar I5 and the members adjacent thereto. Guide lugs or means not shown should also be provided to hold the sliding strip I5 in place, The other members shown have the same numbers and are the same as described in Figure 1.

Figure 4 shows an enlarged isometric view of a portion of the slide strip I5 and its component parts. This being one form of the assembly only, and notthe only construction possible. The strip It has spaced slots ll which correspond to the slots I4 in the sand-trough member ID. Web members I8 are used to attach the rod le to the strip I5 and may be welded in place.

To give an example of the operation and usefullness of the improvement comprising the invention, it will be assumed that a bank of tubes I in a chamber 2 are to be heated as part of the process step in butane dehydrogenation. tubes I are filled with a suitable catalyst and have butane circulating therethrough, such that a dehydrogenation of the butane takes place at high temperature from 1000-1l00 F. Hot combustion gases are admitted to the cell through inlet duct 4; and because of baiile plate 8 and the sand-seals II are forced to flow through the sleeves 3 around the tubes I. The sleeves 3 provide equal circumferential heating to and throughout the length of the tube l. The temperature of the hot gases entering duct 4 is approximately 1400" F. and the temperature of the gases after contact with tubes I is approximately 1120 F. If there were no Jacket provided within the cell, the outer rows of tubes I would be cooler than the inner tubes I because these outer tubes would contribute by direct radiation the larger part of the heat loss from the exterior walls of the chamber. However, with the jacket I 2 provided, the how of hot gases entering heated space i8 through slots I4, is so regulated as to maintain the Jacket I2 temperature approximately equal to the temperature of sleeves 3 in the outer rows of tubes I. Hence, since there is no temperature difference, there is no loss of heat from these sleeves 3 to the Jacket i2, and

tubes I operate at the same temperature, with all the heat loss from the chamber exterior walls being supplied by the stream of heating gases flowing in space 53. It is desirable that the spacing of Jacket I2 from the exterior walls of the chamber be as small as will permit sumcient gas to flow through space I3, at the available pressure drop from top to bottom of sleeves 3, to supply the heat loss through the exterior walls and maintain Jacket I2 everywhere at approximately the same temperature as sleeves 3. If a greater spacing than this is used, then an excessive flow of hot gas must be passed through space I3 to maintain jacket I2 and sleeves 3 at approximately the same temperatures. The control of the flow of the gases to this space I3 is by means of the slide strip or strips I5, which operate to open and close or have partially open, the slots I4. The handles IS on the rods IB which extend through the Wall, provide means outside the cell to adjust the air openings. The hot gases bypassed to this space I3, and through the tubes 8 discharge to the bottom of the cell 2 and then are withdrawn by means of duct 4.

It is. of course, very desirable from the process point of view to have all tubes in the bank heated equally to obtain as uniform a dehydrogenation and reactivation of the products as is possible. Assume a 5" thick wall of insulating material for the cell having a conductivity of 0.13 B.t.u per square foot, per F'., per foot, per hour, also assume that the jacket I2 is spaced from the wall 5 approximately 1"; then for a commercial size unit with cell 2 being approximately 10 feet in height, it may be shown that with about 10% of the hot flue gases charged to the unit being shunted to space I3, the tubes can be maintained at substantially equal temperatures. Calculations show that with 1400 F. inlet gases. the gas The come so great. In the reactivation process gas with controlled oxygen content is charged to the tubes I in order to burn off carbon deposit on the catalyst within. This process is exothermic so that the flue gases, on the outside of the tubes entering the chamber 4 and the sleeves, 3 act to carry away excess heat, being charged to the cell at about 820 F. and being withdrawn at about 900 F. For this reactivation period, conditions are not as critical as for the processing period; however, here again the jacket eliminates much of the conduction and radiation losses of the wall, and gives a more equalized condition.

The description of this inventionand examples of operation have been directed to the dehydrogenation of butane. However, other processes such as hydrogenation, catalytic cracking, etc., wherein heat exchange occurs in a chamber or cell similar to that described, may well make use of the invention to obtain equalized conditions.

I claim as my invention:

1. A heat exchange apparatus comprising a chamber having side walls and end walls, a bank of tubes extending through said end walls and the chamber, a partitioning member extending across the chamber and forming an inlet compartment with one of said end walls and a heating compartment with the other of said end walls, a sleeve concentric with and spaced from each of said tubes and extending through said partitioning member, said sleeves terminating short of said end walls and being open at their opposite ends. a plate parallel with said tubes and sleeves extending from said partitioning member adjacent but spaced from one of said side walls within the heating compartment and disposed outside said tube bankand forming with the side wall a jacket communicating with the interior of the heating compartment adjacent the end thereof opposite the partitioning member, said partitioning member being .apertured between said plate and the last-mentioned side wall to provide communication between said inlet compartment and said jacket, means for introducing a fluid heating medium to the inlet compartment and means for removing said medium from the heating compartment.

2. The apparatus as defined in claim 1 further characterized in that the apertured portion of said partitioning member is provided with adjustable means for controlling the flow of heating medium from the inlet compartment to said Jacket.

CHARLES C. WATSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'I'ENTS Number Name 7 Date 826,773 Engleitner July 24, 1906 2,024,828 Levine Dec. 17, 1935 FOREIGN PATENTS Number Country Date 11,180 Leek (Australian) Jan. 9 1928 

